 
 ;; In developing the time period conversion functions, we noticed that
 ;; as long as the time period remained consistent from dataset to
-;; dataset, the ability to 0-index became irrelevant.  Our choice of
-;; January 1st, 2000 ensures that, regardless of the date on which the
-;; specific MODIS product became active, datasets at the same temporal
-;; resolution will match up. With that in mind, we chose January 1st
-;; 2000.
+;; dataset, the ability to 0-index each dataset became irrelevant.
+;; Our choice of January 1st, 2000 as a common reference date ensures
+;; that, regardless of the date on which the specific MODIS product
+;; became active, datasets at the same temporal resolution will match
+;; up.
 
 (def ref-date (date-time 2000))
 

;; first of each month, while the others mark off blocks of 16 or 8
;; julian days from the beginning of the year.
;;
;;(It's important to note that time periods are NOT measured from the
;; activation date of a specific product. The first available NDVI
;; 16-day composite, for example, has a beginning date of February
;; 18th 2001, or Julian day 49, the 1st day of the 4th period as

    (+ (* years (per-year unit span))
       (quot units span))))

;; The following partial functions take care of the issue with delta
;; above, by calculating the span in periods across years.

(def months (partial delta-periods month 1))
(def sixteens (partial delta-periods julian 16))
(def eights (partial delta-periods julian 8))

;; We currently choose the period-func based on the resolution of the
;; data. This will have to be amended, as some datasets at different
;; temporal resolutions do indeed have the same spatial resolution.

(def period-func
  {"1000" months
